Each nephron consists of functionally distinct segments of tubule cells. While the functional characteristics of each nephron segment being well defined, the metabolic characteristics have been poorly defined. In this project, studies will be carried out to characterize the cell metabolism in an isolated, defined segment of single nephron, and then to evaluate the ionic and hormonal regulation of the cell metabolism. More specifically, the following experiments will be done in each defined nephron segment, i.e., glomerulus, proximal convolution, thick ascending loop of Henle, distal convolution, and cortical collecting tubules. 1. Define the basic metabolic characteristics: glucose oxidation to gluconeogenesis, other substrates oxidation, etc. 2. Examine effects of changes in ionic composition in the extracellular milieu on cell metabolism. 3. Examine changes in cell cyclic AMP and cyclic GMP in response to parathyroid hormone and other hormones. 4. Determine the effects of hormones and cyclic AMP and cyclic GMP on the cell metabolism in each hormone-sensitive segment of nephron. 5. Determine the sites of action of insulin along the nephron. These studies will provide further information on the characteristics of renal cell metabolism in each defined nephron segment, and its control by ions and hormones. The studies may help understand the mechanism and sites of action of hormones along the nephron.